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Feb. 7, 19 56 L. R. RAHSON ELECTROMAGNETIC TIMING nzvzcss 3 Sheets-SheetOriginal Filed Nov. 9. 1945 L w 3 0" mrr w WM H J y/ W u M r y a m 6Feb. 7. 1956 L. R. RANsoN ELECTROMAGNETIC TIMING DEVICES Original FiledNov. 9, 1945 3 Sheets-Sheet 3 INVENTOR. l/oya 4 055 c// lfanson BY/ZZ/V! HTTO/F/VE) United States Patent ELECTROMAGNETIC TIMING DEVICES LloydRussell Ranson, Charlotte, N. (3., assignor to .The

Clark Controller Company, Cleveland, Ohio, a corporation of Ohio 6Claims. (Cl. 317-178) This invention relates to electro-magneticallyoperated timing devices, and particularly to electro-magnetic timingdevices by which a time interval is introduced between the moment ofenergizing an electromagnetic winding and the moment at which themagnetism produced by the winding performs a useful function oroperation.

In general the embodiment of the invention comprises an electro-magneticwinding; and an air gap or work gap through which magnetism, or magneticflux produced by the winding, acts to perform a useful operation; andmeans to cause the magnetic flux in the work gap to be too weak toperform the operation at the moment when the wind ing'is first energizedand to cause the strength of the'flux in the work gap to graduallyincrease to the operating value at a controlled or timed rate.

The invention is applicable to numerous uses in various arts; but one ofits most important uses or functions is to time or delay the operationof electro-magnetically operated electric switches or contactors; andfor that reason it will be illustrated and described herein as appliedto that use.

'It is among the objects of the invention:

To provide generally an improved timing and operating device of theclass referred to above;

To provide generally an improved electro-magnetically operated apparatustimed to operate with delay in an improved manner;

To provide an improved electro-magnetically actuated apparatus in whichan operation is magnetically performed after the elapse of a timeinterval following energization-ot' an electromagnetic winding, bymagnetic pull on a movable element; and in which the magnetic pullincreases at an accelerating rate having improved characteristics as thetime interval goes on.

Other objects will become apparent to those skilled in the art to whichthe invention appertains.

The invention is fully disclosed in the following descripr tiontaken inconnection with the accompanying drawing, in which:

Fig. 1 is a side elevational view partly broken away and in section ofan electric contactor, and showing in side elevation a timing andoperating device embodying a part of my invention applied thereto;

Fig. 2 is a view showing the timing and operating device of Fig. 1 inlongitudinal section, and to a larger scale than in Fig. l, and withparts of Fig. 1 shown fragmentarily;

Fig. 3 is a fragmentary view similar to Fig. 2 showing parts indifierent operative positions; and showing a modification;

Fig. 4 is a view similar to Fig. 1 showing a modification;

Fig. 5 is a view to enlarged scale of a part of Fig. 2 showing anadjustment which may be employed for a valve device of Fig. 2;

Fig. 6 is a diagrammatic view illustrating certainmaghero-dynamicproperties both of the invention and of certain prior art;

2,734,152 Patented Feb. 7, 1956 Fig. 7 is a view generally similar toFig. 1 showing another kind of valve device which I may employ;

Fig. 8 is apfragmentary view showing a modification which I may employof an attaching and securing device of Figs. 2, 4 or 7.

In the patent to Charles H. Rippl, issued October 8, 1929, No.1,730,688, is disclosed anelectric contactor providedwith a delaying ortiming and operating device in the same general class as thatrofrthepresent invention; and the present invention when applied to an electriccontactor, may be considered as an improvement over the disclosure-ofthat. patent. Referring to that patent, when the winding20 isenergize'dby a predetermined potential, a predetermined flux strength develops inan air gap or work gap-between the contactor-arm 16 and the adjacent endof a magnetic: plunger-35, enclosed in and movable in asealedoil-containingchamber 2,8 madesof non-magnetic material.

The magnetic pull of the flux in this gap tends to move the contactorarm 16 to close the contacts 12-14, but is insufiicient to do so,because ofthe length and reluctance of the long air gap and theconsequent weakness of thejflux.

This magnetic pull, however, is great enough to pull the plunger 35forwardly in the chamber 28 against the opposing force of aspring37,;and it moves forwardly, its movement being retarded by a flowrestricting valve arrangement at the rear of the plunger, through whichoil displaced by the moving plunger is caused to flowv As the plunger:35 movesforwardly it reduces the length of the air gapbetweentheplunger end and the contactor arm 16; and this causes the fluxto gradually increase in theair gap and exert increasing'pulling forceon thearm; and a point is reached inthe movement of the plunger andafter a predetermined time interval of movement, at which the pull isgreatenough to operate the contactor arm andclose the contacts 12-14.

The mechanical load operatively moved by the'fiux is in two parts; theinitial load of starting the arm 16 to move against its bias; and thefinal load of forcing the contacts 1 214 together into pressureengagement at the end of the arm movement.

This contact engaging force must be suflicient to enable the contacts tocarry the desired current; and sufiicient to prevent the contacts fromseparating or vibratingone upon the other when theyfirst engage with ablow or thereafter when the contactor as a whole is subjected to shocks,which vibration or separation, if it should occur, will drawmomentaryarcs at the contacts and weld them together.

This final-load, or, the minimum force necessary to firmly engage thecontacts and hold them engaged, is a fixed or pre-irnposed quantity forany given size of contacts, whereas the initial load or force to startthe arm 16 moving may be made large or small, and arbitrarily chosen, byadjusting the gravity or other bias holding the arm in normalopen-cantact position.

Now it has been found that, with the arrangement of parts of the saidpatent, the magnetic pull on the arm 16 increases approximatelyrectilinearly with movement of tion, the solid line curve Acorresponding to the full stroke of the plunger from to a.

When, as in practice, the arm 16 is held open by its bias alone and isfree to move, it will start to move when the pulling force is at thepoint b on the curve A corresponding to the position 0--c for theplunger, at which the magnetic pull crosses the bias-load line :1 andoverbalances the bias. Thereafter the arm 16 moves and the plunger 35continues to move, and the working air gap is shortened by bothmovements going on concurrently; and, by the time the contacts areclosed, the pull holding them closed will be at the point e, the pullfrom. b to c rising along the dotted line 1 due to shortening of theworking air gap by arm movement.

From this pull curve A, it will be seen that in order to have at esuflicient magnetic pull and force to hold the contacts securely closed(for the purposes mentioned above) there will unavoidably be arelatively large magnetic pull at b when the arm 16 starts to move,because the pulls at e and b cannot be greatly different due to to theforce b, to hold it open until the timing interval of the moving plungerhas run. The result is that for the sake of having ample contactengaging force, the bias of the arm 16 must be correspondingly great,and the winding must accordingly provide abnormally high ampere turns tomove the arm, and the whole contactor must be of abnormally largeproportions. Another way to say this is, that for a contactor, winding,etc, of given size and cost, there is a low limit to the force availableto hold the contacts closed, and the current carrying rating of thecontacts must be low. Satisfactory operation therefore is attained witha sacrifice of economy.

In order to overcome this economic disadvantage of the device of thepatent a problemis presented.

According to the present invention this problem has been solved bycausing the pull on the contactor arm to be relatively Weak during themajor part of the stroke of the plunger and while the arm is in theopen-contact position; and to become abruptly stronger and rise rapidlyto a high value near the end of the plunger movement, and near the endof its timed interval.

This enables the contactor aim to be held unmoved by any desired bias,or even small bias, and at the same time provides very great contactengaging force.

The present invention and the means by which this result is accomplishedwill now be described.

Referring to the drawing, I have shown in Fig. l, a conventionalelectric contactor provided with an operat ing and timing device 1,which constitutes part of my invention, applied thereto.

The contactor itself comprises a magnetic frame element 2, mounted uponan insulating panel 3, by any suitable number of screws or bolts 4, andhaving a forwardly projecting leg 5, upon which at 6 is pivoted a.contactor arm 7, carrying at its upper end a contact 3,

movable therewith, and engageable, upon movement of the arm, with astationary contact 9, mounted upon a post 10, secured to the panel 3 bymeans of a stud 11, to which electric circuit connection can be made.The contactor arm 7 may be in two parts as illustrated, the contact 8being mounted upon a supplemental arm 13 pivoted as at 15 to the mainarm 7, in a well known whereby the open position of the arm may beadjustably changed.

The arm 7 is preferably provided with a fiat magnetic pole face 23.

The timing and operating device referred to hereinbefore is shown inelevation at 1 and will be more fully described in several forms, but ingeneral it comprises a cylindrical structure 24 Fig. l, disposed in thehollow core of an electro-magnetic energizing winding 25 and has a flatmagnetic pole face 26 opposite the pole face 23 of the arm 7 and spacedtherefrom, providing thereby an external working air gap 27. Rearwardlyof the winding 25 as at 29, the device is of reduced diameter andprojects through aligned bores or holes in the panel 3 and in themagnetic frame element 2 respectively; and the reduced diameter providesa shoulder 30 engaging the frame element 2 to predeterminedly positionthe device as a whole longitudinally. The device is held in thisposition by a bracket 31 mounted upon the panel 3 by screws 32-32 andoverlapping the rearward end of the reduced diameter portion 29, and bya screw 33 projected through the bracket and screwed into the device,and these parts are made so that the shoulder 36 is drawn firmly againstthe frame element 2.

Meeans not shown but well understood in the art is provided to hold theWinding 25 against the frame element 1 in a well known manner.

The operation of the device as a whole will be apparent. When thewinding 25 is energized, magnetic flux is produced in the air gap 27between pole faces 23 and 26, tending to move the arm '7 clockwise, asviewed in the drawing, to engage the contacts 8 and 9. At the time ofenergizing the winding the flux in the gap 27 is insufficient toovercome the bias of the arm 7 to move it, but after the passage of atime interval, determined by the timing device 1 in a manner to bedescribed, the flux strength in the gap 27 increases sufiiciently tomove the arm 7 and engage the contacts. When the Winding is de-energizedthe bias of the arm 7 restores it to its normal position and disengagesthe contacts.

The interior construction and mode of operation of the timing andoperating device 1 will now be described and reference may be had firstto the form of Fig. 2; wherein some of the parts of Fig. 1 have beenreproduced fragmentarily.

A liquid-tight, tubular chamber 34 is provided preferably cylindrical incross section as indicated in the drawing. The side wall comprisesgenerally a forward portion 36 of non-magnetic material such as brass,and a rearward portion 38 of magnetic material such as steel, the twoparts being turned down so as to telescope one within the other at anairtight liquid tight juncture indicated at 39. The inside diameter ofthese two tubular portions is uniform. The outside diameter of the part36 is somewhat greater than that of the part 38 to provide the aforesaidshoulder 30. At the juncture 39, the tubular part 38 may be cut back toprovide a groove 40 which may be filled with solder 41 to seal thejuncture. The rearward end of the tubular chamber is closed and sealedby a plug 42 of non-magnetic material such as brass, screw threaded intothe end of the tubular Wall 38. The plug 42 has a flange 43 overlappingthe end of the tubular wall, and the liquid tight seal effected by theend of the plug and the flange 43 may be further insured by a ring ofsolder 44 sealing the flange 43 and the end of the tube together.

The plug 42 has a threaded hole 45 therein into which the aforesaidscrew 33 is screwed for positioning the device in connection with thebracket 31 as has already been described in connection with Fig. l.

The forward end of the tubular wall 36 is sealed by a plug or pole piece46 of magnetic material, screw threaded into the end of the tube asshown, and the juncture may be further sealed by providing a groove andfilling it with solder as at 47.

The pole piece 46 has the exterior transverse pole face 26 alreadydescribed for Fig. 1. The forward face of the winding described for Fig.1 is'indicated diagrammatically by the broken line 25 in Fig. '2, fromwhich it will be seen that the pole piece 46 projects forwardly out ofthe winding, and projects inwardly into the winding for a substantialdistance. Theinner end of the pole piece .46 has a transverse pole face48 well within the winding.

The flat or planar pole face 26 extends transversely of the axis of thepole piece 46 substantially at right angles thereto; and the pole face23 is substantially parallel to merit with thepole piece 46. Preferablythe pole piece 46 has a recess or bore 53 therein to receive and centerthat end of the spring. The plunger 49 is thus springbiased toward therear of the chamber 34. The plunger at its forward end has a transversepole face 54 parallel to the pole face 48; and thereby is provided amagnetic air gap 55 between the pole faces 48 and 54.

The bore 50 constitutes part of a passageway extending entirely throughthe plunger and at its rearward end this passageway is enlarged toprovide a cavity 56 in the nature of a housing for a valve structure.

At the rearward end of the valve cavity 56 is a cylindrical outlet 57,see Fig. 5, which may be provided in any suitable manner. The meansshown comprises a thimble 58, having a flange 59, seated in an annularrecess in the end of the plunger, the end of the plunger being peenedover the flange as at 60 to retain it in position.

A valve shown generally at 61, is provided with a flange 62 normallyresting upon a shoulder 63 at the forward end or bottom of the cavity 56and normally retained thereon by a spring 64 abutting upon the valveflange 62 and reacting upon the said flange 59. The valve flange 62 hasa transverse passageway or groove 65 therein, affording communicationbetween the bore 50 in the plunger and the cavity 56. Rearwardly of theflange 62 the valve is provided with a slightly conical throttle portion66 axially aligned with the cylindrical outlet 57,

and guided to enter it by a flange 67 on the valve, disposed in thecylindrical outlet'5 7. To prevent the flange '67 from obstructingthecylindrical outlet 57, it is preferably made circular to slidingly fitthe outlet and then flats are cut on its periphery as shown in thedrawing.

In assembling the parts of Fig. 2, the pole piece 46 may be screwed intothe chamber 34 and sealed therein as described. The valve parts may beassembled with the plunger 49, as a unit. A measured quantity of oil orother suitable liquid is put into the chamber.

The oil is not shown in cross section in Fig. 2 to avoid obscuring theparts of the structure, but is indicated by its level at 106 in theworking air gap 55; and it is believed that this will make clear thepresence of the oil in the gap 55, bore 50, cavity 56, etc. particularlyin view of the aforesaid prior patent. The same indication of the oilhas been made in Figs. 3, 4 and 7 to bereferred to. The spring 52 andthe assembled plunger are then put into the chamber and the end plug 4is screwed in and sealed as described.

The operation of thedevice of .Fig. 2, and in connection with parts ofFig. 1 fragmentarily shown therein, is as follows. The plunger 49 isnormally spring-biased to the rear of the chamber 34 by the spring 52,the end 60 abutting against the plug 42. When the winding 25 isenergized with predetermined ampere-turns for example by being connectedacross a source of potential, mag netic flux appears in the air gap 27between the pole faces 23 and 26, and in the air gap 55 between the polefaces 48 and 54. At the predetermined ampere-turns, the pull of the fluxin the gap 27 is not enough to overcome the bias of the arm 7, but thepull of the flux in the gap 55 of the plunger 49 is enough to overcomethe'bias produced by the spring 52, and the plunger 49 moves forwardlyin the chamber 34. As it moves it displaces oil from in front of it, andrearwardly through the bore 50, where it-impinges upon the valve 61;thence transversely through the groove 65, into the cavity 56, andthence through the cylindrical outlet 57, the displaced oil moving intothe space 68 rearwardly of the plunger (see Fig. 3, wherein the plungeris shown in a forwardly moved position).

The movement of the plunger is retarded by the valve arrangementdescribed above. The pressure of the dis placed oil on the valve flange62 compresses the spring 64 and moves the conical valve portion 66 intothe cylindrical outlet 57, one position of which is shown in Fig. 3,throttling the flow through the outlet'57. The more rapidly the plungertends to move the morethe flow is throttled, and the result of which isthat the plunger moves forwardly at a retarded timed rate.

As the plunger moves forwardly and shortens the length of the interiorair gap 55 between the pole faces 48 and 54 within the winding, thereluctance of the magnetic flux path as a whole decreases, and the totalflux accordingly increases, and the pull in the gap 27 on the arm 7increases, and finally reaches a value at which the arm 7 is movedagainst its bias to close the contacts of the contactor as described forFig. 1.

A characteristic curve of pull on the arm 7 is shownat the curve B inFig. 6, the solid line curve B showing the pull on the arm in the gap 27for the fullstroke of the plunger, with the contactor arm experimentallyheldin below the bias-load line d than the curve A of the prior artdevice; but that nevertheless the curve B because of its abrupt upwardsweep, crosses the bias-load line; this occurs at i when the plunger hasarrived at j. I

In practice, after the plunger arrives at j, the contactor arm 7, movesto closed position, closing the external work gap 27; and the plungercontinues to move concurrently therewith; with the joint result that thepull on the arm rises higher than the point h, or to the point k, due tothe closing of the gap 27.

Thus the plunger has a longer movement for timing purposes with thecurve B than with the curve A, and the final pull it to hold thecontacts closed is much greater than that at e for the curve A; both dueto the abrupt upward sweep for the curve B. I

It will be apparent that if that part 0c of the stroke of the plungerwere suflicient for timing in any given case, then a bias-loadas low asthe dotted line I could be used and the switch closing load would bemade accordingly smaller, and the contactor stillmore economical,without any reduction in the high contact closing 7 and holding pull k.

It is believed that this sudden rise of pull in thelatter part ofmovement of the plunger may be explained as follows.

As will be apparent from the drawing, the flux produced in the core ofthe winding 25 when it is energized-,flows contactor arm 7; and thenuwardly through the frame element 2 to the rear end of the winding 25.The pole piece 46, where it projects forwardly out of and beyond thewinding has no laterally extending portions that might divert fluxlaterally out of the said serial path, so that all of the flux in thepole piece is directed thereby to flow directly axially across the workgap 27 and into the arm 7. Because the pole piece 46 extends well intothe winding 25, practically all of the flux developed by the windingwill flow longitudinally through this pole piece and appear at the poleface 26 and in the gap 27. But with a large internal air gap 55, thetotal flux is relatively weak and there will be, accordingly,considerable dispersal or fanning out of the flux in the gap 27, andthis weak flux, acting on a large area, produces little pull on the arm7.

Throughout the major part of the movement of the plunger, increments ofplunger movement decrease the internal air gap very littleproportionally, so that the total flux increases very littleproportionally; and the distribution of the flux remains substantiallythe same, being distributed thinly or at low density over the pole face26, and the cross sectional area of the working flux in the gap 27 doesnot change materially; and the pull in the gap 27 increases very little;and the pull remains weak.

There is however, a critical point in the plunger movement at which twothings occur: first, the internal air gap 55 has then become so smallthat for small increments of plunger movement there is a rapidproportional reduction of the air gap and a rapid proportional increaseof total fiux and density to higher values; and second, as the fluxincreases to higher values, it attains the characteristic sometimescalled stiffness and the flux in the gap 27 ceases to be fanned out butin eifect concentrates in the gap 27 and this both further increases itsdensity, and reduces its active area.

There is thus a critical point in the movement of the plunger at whichthe fiux in the gap 27 begins to increase rapidly (which rapidlyincreases its density); and at which the flux pattern in the gap becomesless fanned out which latter not only still further increases the fluxdensity, but also decreases its active area.

As is well known, the pull in a magnetic air gap is represented by thecross sectional area of the acting flux multiplied by the square of theflux density. So that this double increase of density in the air gapaccompanied by a decrease in air gap area, effects an abrupt oraccelerating increase in the pull as shown in the curve B, as the end ofthe plunger approaches closely to the pole piece 46.

The above described action is diflerent from that in the said priorRippl patent, as shown in the pull curve A. In the patent, when theplunger is in the rearward position, and there being no magnetic polepiece ahead of it, and accordingly no interior magnetic air gap, theflux from the end of the plunger bends laterally and flows into andthrough the magnetic ring 23a, and the flux acting on the arm 16 actsthrough an annular magnetic gap having the small area of: the ring. Thismakes the pull strong, because of high density in small area. As theplunger moves forwardly it is true that the flux density as a wholeincreases, but when the plunger moves forwardly it enters the ring 28a,and the greater part of the flux no longer bends laterally into the ringbut goes straight ahead toward the arm 16, so that the flux then isdistributed over a circular air gap of large area. The pull on the arm16 thus does not increase at an accelcrating rate due to the increasedflux, because of the concurrently greatly enlarged area of the workinggap.

The modification of Fig. 4 is similar to the form of Fig. 2 abovedescribed except for features of detail which in some cases may bepreferred. In this form, a forward pole piece 69 is fitted into theforward end of a brass or other non-magnetic tube 70.

A groove 71 in the pole piece has a wire 72 of brazing 8 material placedtherein before the pole piece is inserted into the tube and the fit atthis end of the tube is made leak-proof, by heating the parts(preferably by induction heating) to melt the wire 72 and braze theparts together.

At the rearward end of the tube 70 it is closed by a metal head 73seated in an annular recess in the end of the tube, and sealed by a ringof solder or brazing material 74. A stud 75 is threaded through the hole76 in the axial center of the head 73 and upon its inner end the guidinghead 67 of the valve abuts, and this constitutcs a stop for the plunger49 at its rearward or biased position. A nut 77 on the stud cooperateswith the aforesaid bracket 31 to position the device by drawing ashoulder 30 on the tube 70 into engagement with the frame element 2 asdescribed hereinbefore. This shoultier fail may be formed on the outsideof the tube 76 but I prefer to provide it by a separate tubular sleeve78 loosely telescoped over the outside of the tube 70, and by providinga shoulder 79 on the pole piece 69 against which the other end of thesleeve abuts, the shoulder 79 overlapping the ends of both the tube 70and the sleeve 78.

The provision of the threaded stud 75 provides a number of advantages.

in assembling the device, the plunger 4h and its valve structure and thespring 52 are first put into the tube 70. The head 73, and without thestud 75 therein, is then placed in position and sealed by the sealingring 74. While as stated this ring may be made of soldering material, itis preferred to use a wire of brazing material and to heat it to asufliciently high temperature to melt it. This may conveniently be doneby electric induction heating. Because of the high temperature of suchheating, the air within the tube 70 would otherwise produce pressurewithin the tube but because of the threaded opening 76 in the head 73,the pressure within the tube remains at atmospheric pressure.

Oil is now poured into the tube 70 through the threaded opening 76sufiicicnt to provide the aforesaid level 106. Then the stud 75 isscrewed into the opening, and, having a close fit with the threadedopening 76, is practically oilleak proof. The device may now be mountedin opera.- tive position in the contactor and the contactor operated andthe timed delay of its operation observed. The rear ward retractedposition of the plunger 4-9 is stopped upon the stud 75 as described;and by turning the stud '75 by means of screw slot M5 in the outer endthereof, the re tractcd position of the plunger 49, and accordingly thelength of the air gap 5%, may be adjustably changed, and this obviouslywill sheet a change in the length of the time interval required for theplunger 49 to move forwardly to the point at which the arm 7 is moved;and the period of delay of the operation may thereby be adjusted.

By means of this adjustment, a number of such devices, produced at thesame time in production, may be caused to all have the same timeinterval of delay, and any differences in the delay time which mightresult from slight differences in dimensions, winding ampere turns,etc., may all be eliminated, and a quantity of such devices may all beadjusted to be uniform in operating interval.

After this adjustment has been made, then the threaded opening 76 may befinally and hermetically sealed by a ring hit of solder or the likeapplied to seal the stud 75 the head 73.

Thereafter the stud 75 may be used in connection with the bracket 31,and a nut 77 screwed on to the stud 75 as shown in Fig. 4 to finallymount the device, with the shoulder 39 drawn tight into engagement withthe frame element 2, as described above.

It will be observed that the form of Fig. 4 eliminates a number ofmachining operations which are necessary in the form of Fig. 2.

in either of the forms of Fig. 2 or 4, the rate at which the plunger 49moves forwardly, under control of th e valve structure, will depend uponthe response of the valve to the pressure of dispiaced oil upon it andthis in turn is determined by the strength of the spring 64. In Figs. 2and 4, this spring is shown as abutting upon the flange 59 of thethimble 58. While this spring can n production be made in quantities ofsubstantially 11111- form strength, in some cases it may be desired toprovide an adjustment for it and this is shown in Fig. 5. A number ofthin metal shims 83-83 are provided and placed between the spring endand the flange 59, and by selectively varying the number of the shims,the compression and strength of the spring can be adjustably varied.This is done before the end of the tube is permanently peened over at60.

In Fig. 2 or 4, it will be observed that when the winding 25 isde-energized and the contactor arm 7 is moved to its biased position,ready for another operation, the magnetic flux in the gap 55 dies outand the spring 52 propelsthe plunger 49 rearwardly to its originalposition and displaces the oil from the rearward end of the plunger backto'the forward end, and the valve is immediately opened by the spring 64to full open position which allows the plunger to return immediatelywithout delay.

In Fig. 7 is illustrated a modification similar in construction andoperation to either of the forms of Fig. 2 or 4 but in which the valvearrangement is operated magnetically.

In this form (for which in view of Figs. 2 and 4 a brief descriptionwill now sulfice) the valve comprises a stem 84 of magnetic material,slidable in a bore 85 along the axis of the plunger 86 with ampleclearance with the bore wall as at 87. The stem 84 projects forwardlyfrom the forward end of the plunger as shown at 88. The forward endportion of the bore 85 is enlarged as at 89 providing a bore shoulder 90and the plunger retracting spring 89 loosely surrounds the setrn 84 andreacts on this shoulder.

At the rear end of the plunger bore 85 it is flared out into a conicalvalve seat 91; and beyond the valve seat is an enlarged cavity 92 closedat its outer end by a head 93.

The stem extends into the cavity and has a conical valve portion 94' tofunction as a valve, in cooperation with the valve seat 91; and beyondthe valve portion the stem has a flange 95adjustably screw threadedthereon, and between the flange 95 and the bottom 96 of the cavity 92 isa compression spring 97 the tension of which is adjustable by moving theflange 95. The head 93 has a central perforation 98 therethroughcommunicating with the cavity 92 through a T-shaped passageway 99 in thestem, when the stem rests on the head 93 as it normally does, orcommunicating with the cavity directly when the stem end is raised fromthe head in operation as will be described.

In operation, flux produced in the inner air gap 55 by the windingindicated at 25 as for the other forms, acts on the end 88 of the stemand pulls the stem forwardly against the tension of the spring 97, atthe same time that flux in the gap 55 pulls the plunger 86 forwardly.The oil in the chamber 100 (indicated at 106) displaced by forwardmovement of the plunger, flows rearwardly through the bore 85 andthrough the conical valve 91-94 being variably throttled thereat for thepurposes described for the preceding forms.

For any predetermined energizing ampere turns and flux, andcorresponding adjustment of the spring 97, the valve will be pulledforwardly to a definite position and will predetermine a rate ofmovement for the plunger, by throttling the oil flow to a predeterminedrate.

If for any reason the ampere turns should increase (or decrease) forexample due to a change of energizing voltage on the winding 25, thevalve stem will be pulled magnetically farther forward againstincreasing tension of the spring 97 (or retracted farther rearwardly bythe spring 97), and will thus compensate for the change of ampere turnsand maintain the rate of oil flow and rate of plunger movementunchanged.

And if the ampere turns should increase (or decrease) at differenttirnesbecause of a change of temperature and the resulting change ofresistance of the winding, a like compensation will be effected.

This form is therefor preferred when constant timing is wanted undercircumstanceswhich may cause the ampere turns of the winding to vary.Otherwise the mode of operation and construction is the same asdescribed for the other forms.

In general, as tothe several forms, it is preferable for the maintubular chamber wall to be of non-magnetic material in order not todivert any of the magnetic flux out of the working air gap 55. Thechamber wall rearwardly of the gap 55 however can be made of magneticmaterial, and the reluctance of .the magnetic circuit as a whole willthereby be decreased with advantages of economy; and that is the purposeof the magnetic rear wall portion 38 of Fig. 2.

Obviously therefore, the entire chamber wall of Fig. 2 could benon-magnetic; or the rear portions of the chamber walls of Figs. 4 and 7could be magnetic.

In either case, the main part of the flux from the winding and in theplunger 49 flows from the plunger into the return path providedby theframe element 2, following in general the dotted line 107 of Figs. 2, 3,4 or 7; and there will be some magnetic attraction between the plunger49 and the frame element 2. When the rear part of the chamber wall isnon-magnetic as in Figs. 4 and 7, this attraction is negligible, becauseof the large gap provided by the thickness of the non-magnetic wall.

But when the rear part of the wall is magnetic (for the advantages notedabove) this air gap -is very thin, being that onlyof the sliding fitclearance between the plunger 49 and the wall, and the attraction isaccordingly greater and may in some cases cause the plunger to dragfrictionally'on the wall and make it irregularinits movement.

In such cases therefore it may be desirable to artifically increase thisgap, and this may be done as shown in Fig. 3 as a modification, whereina sleeve of non-magnetic ma terial, 108, is fitted upon and around theplunger, moving therewith. It has been found that a very thin sleeve 108will serve the desired purposes and that it may be provided by platingnon-magnetic metal on the plunger.

' In Fig. 4 is shown another modification which may be utilized in allof the described forms. A thin non-magnetic washer 109 is'sp'ot weldedupon the pole face 48 of the pole piece 69 to prevent magnetic stickingof the end of the plunger 49 on the pole piece after the plunger hasengaged it at the end of its stroke. A

In-Fig. 8 is illustrated amodification which may be used in place of theabove described bracket31 to hold the timing device rearwardly againstits shoulder 30 forthe purposes described. A tube 101 is looselytelescoped over the'rear end of the timing device 1, and projects beyondits outer end as at 102. The inner end 111 ofthe tube 101 extends withample clearance through a hole 110 in the panel and abuts upon the frameelement 2. A disc or transverse bar 103 lies on theouter end 102 of thetube 101. A stud or screw 104 attached to the device as above describedprojects through a perforation in the disc, and a nut on the stud, whenscrewed up tight, draws the device 1 rearwardly and engages the shoulder30 with the frame element 2 and clamps the tube 101 between the'disc 103and the frame element 2 into a rigid assembly. Means otherwise tosupport or mount the tube 101 and disc, 103 are unnecessary. With thisarrangement the same parts may be used with different thicknesses ofpanel 3.

My invention is not limited in all respects to the exact construction,proportion of parts, etc., illustrated and de scribed; and certainly notto its application to an electric 'contactor, norm theparticular'contactor of the draw- 11 ing; and my invention iscomprehensive of all changes and modifications which come within thescope of the appended claims.

This application is a division of application Serial No. 627,735 filedby me November 9, 1945, for Retarded Electromagnet, now Patent No.2,605,327.

I claim.

l. In a magnetic timing device, a closed tubular chamber; liquid in thechamber; a winding surrounding at least a portion of the chamber; amagnetic plunger reciprocable in the chamber; means providing an air gapin the chamber at the forward end of the plunger causing the plunger tomove forwardly responsive to winding-induced magnetic flux in the gap; aspring tending to retract the plunger; a passageway through the plunger;a valve seat at the rear of the passageway; a valve cooperable with thevalve seat; a valve spring tending to hold the valve away from the valveseat; whereby forward movement of the plunger causes liquid to flow fromin front of the plunger through the passageway to the rear of theplunger; a valve stem in the passageway, connected at its rearward endto the valve, and having a magnetic forward portion responsive to bepulled forwardly by said windinginduced flux to move the valve towardthe valve seat in opposition to the valve spring, to throttle the liquidflow and correspondingly retard forward movement of the plunger.

2. In a magnetic timing device, a chamber comprising a non-magnetictube, closed at its forward end by a magnetic pole piece projectingthereinto; a closure for its rearward end; liquid in the chamber; amagnetic plunger reciprocable in the chamber and normally retracted by aspring; the space between the forward end of the plunger when retractedand the pole piece providing a work gap; which by a winding surroundingthe tube may induce magnetic flux in the air gap and propel the plungerforwardly; a passageway through the plunger; a conical valve seat at therearward end of the passageway; a conical valve cooperating with thevalve seat; a valve spring normally holding the valve away from theseat; whereby forward movement of the plunger causes liquid to flow fromin front of the plunger through the pas sageway to the rear of theplunger; a valve stem of magnetic material disposed in the passagewaywith clearance space around it; and connected at its rear end to thevalve and at its forward end projecting into the air gap, and propelledforwardly by flux in the air gap to move the valve forwardly to throttlethe liquid flow and correspondingly retard forward movement of theplunger.

3. In a magnetic timing device, a closed tubular chamher; liquid in thechamber; a magneticplunger reciprocable in the chamber; means providinga magnetic air gap at the forward end of the plunger whereby magneticflux electromagnetically induced in the plunger will pull it forwardly;a spring tending to retract the plunger; a passageway through theplunger; a valve and valve seat disposed at a rearward portion of thepassageway; spring means tending to hold the valve away from the valveseat to maintain the passageway open; whereby forward movement of theplunger causes liquid to flow from in front of the plunger through thepassageway to the rear of the plunger; an element connected to the valvehaving a magnetic portion disposed to be pulled upon by said flux totend to move the valve in the direction to close the passageway inopposition to the valve spring, to throttle the liquid flow andcorrespondingly retard forward movement of the plunger.

4. An electromagnetic structure comprising a winding and ferrous polematerial, for operatively moving a biased armature load by flux producedby the winding in a work air gap between an external pole face on thepole material and a corresponding load face on the load; means effectiveupon energizing the winding to cause magnetic flux and pulling force todevelop in the work gap and to increase during a predetermined timeinterval from values incapable of moving the load, to values which movethe load, and to cause the increase to go on at substantially one rateduring a first part of the interval and at a rapidly accelerating rateduring the latter part of the interval, said means comprising a supportfor the winding to position it with its axis intersecting the load face,and supporting the pole material coaxially of the winding; the polematerial having its said external pole face, transverse to the axis andforwardly of the forward termination of the winding; and the polematerial formed to provide an inner pole face transverse to the axis andwithin the winding and between the ends of the wind ing; a normallyrearwardly spring-biased forwardly movable plunger of magnetic material,and means on the support for guiding its movement axially of thewinding; the plunger formed to provide a plunger face transverse to theaxis and normally spaced from said inner pole face to provide a plungerfiux gap; the winding when energized producing flux serially in theplunger, the plunger gap, the pole material and axially through thelatter; the plunger being movable forwardly against its bias by flux inthe plunger gap; means to retard forward movement of the plunger; theferrous pole material forwardly of the winding being without lateralferrous flux conducting portions whereby the flux therein is caused toflow through the pole material and directly across the work air gap andinto the face on the load in concentrated condition without anyreduction of the flux concentration by lateral ferrous conduction offlux.

5. An electromagnetic structure comprising a winding and ferrous polematerial, for operatively moving a biased armature load by flux producedby the winding in a work air gap between an external pole face on thepole material and a corresponding load face on the load; means effectiveupon energizing the winding to cause magnetic flux and pulling force todevelop in the work gap and to increase during a predetermined timeinterval from values incapable of moving the load, to values which movethe load, and to cause the increase to go on at substantially one rateduring a first part of the interval and at a rapidly accelerating rateduring the latter part of the interval, said means comprising a tubesealed at both ends, and at least the forward end portion of which is ofnon-magnetic material; the winding telescoped over the non-magneticportion; a support for the tube to position the winding with its axisintersecting the load face; the tube supporting the pole materialcoaxially of the winding; the pole material having its said externalpole face transverse to the axis of the winding and forwardly of theforward termination of the winding; the pole material formed to providean inner pole face transverse to the axis of the winding and Within thewinding and between the ends of the winding; a normally rearwardlyspring-biased forwardly movable plunger of magnetic material slidable inthe tube and formed to provide a forward plunger face transverse to thewinding axis, normally axially spaced from the said inner pole face toprovide a plunger flux gap; the winding when energized producing fluxserially in the plunger, the plunger gap, the pole material and axiallythrough the latter; the plunger being movable forwardly against its biasby flux in the plunger gap; a passageway extending through the plunger;a quantity of liquid in the tube some of which is in the plunger gap;the liquid in the plunger gap being displaced and flowing through thepassageway by forward movement of the plunger, and means throttling theflow of liquid to retardthe forward plunger movement; the ferrous polematerial forwardly of the winding being without lateral ferrous fluxconducting portions whereby the flux therein is caused to flow throughthe pole material and directly across the work air gap and into the faceon the load in concentrated condition without any reduction of the fluxconcentration by lateral ferrous conduction of flux.

6. The apparatus described in claim 5 and in which 14 the means tothrottle the flow of liquid is a port at the References Cited in thefile of this patent rearward end of the passageway arid a spring pressedUNITED STATES PATENTS valve holdlng the port open and sub eeted topressure of liquid in the passageway, and the valve is movable against1,292,003 9 1919 the force of the spring by the liquid pressure tovariably 5 1,4183% F June 1922 Partly C1086 the port 1,730,688 Rlppl 069 2,360,922 Wilckens Oct. 24, 1944

